More hospital groups around the country are introducing infection control measures with the number of people hospitalised with flu standing at 1,034.
This represents an increase of 17 from New Year's Eve and an overall increase of 632 on this day last week.
Sixty-two of those in hospitals are being treated in intensive care units, with 26 of them requiring ventilators.
Hospitals across the west and northwest are treating 166 patients with flu, putting services under pressure.
The Saolta University Healthcare Group has introduced mandatory mask-wearing at hospital emergency departments in Galway, Mayo, Sligo and Donegal.
Visitors to other sections of the hospitals and other medical residential settings are also being encouraged to wear masks.
Anyone who is ill or feeling like they are suffering a head cold are being urged to stay away from hospitals to protect sick patients.
Visitors restrictions are being introduced which vary from hospital to hospital depending on the levels of infection in each ward.
Family members of patients, who are considering visiting, are being advised to check with the hospitals in advance.
IMO President Dr Denis McCauley called the current flu crisis "a predictable event".
The Irish Medical Organisation has called for healthcare to be at the centre of government formation talks and programme for government
"It's a very significant event for each person who is now presently in hospital but we should be prepared for this. Every year we're being told that there’s more money going into health... but my concern is it’s not being planned."
Speaking on RTÉ’s Drivetime, he said that increased spending "was great, but unfortunately we have to plan to have a consultant-led system".
The Health Service Executive said that any visitor restrictions will be temporary but are necessary.
Mandatory mask-wearing has already been introduced for all staff and patients at hospitals across Cork and Kerry.
It is now in force at University Hospital Limerick.
Visitors to Ennis, Nenagh, St Johns and Croom hospitals are also being strongly encouraged to wear masks.
